Electrolytic condenser



R. D. MERSHON ELECTROLYTIC CONDENSER Original Filed Dec.A 5l, 1925 Aug.30, 1932.

' Patented Aug. 30, 1932 l UNITED STATES IPATENT OFFICE RALPH D.MERSHON, OF NEW YORK, N.

ELECTROLYTIG GONDENSER Original application tiled December 31, 1925,Seria1`No. 78,534.` Patent No. 1,773,492. Divided and this applicationfiled January 25, 1928. Serial No. 249,314. l

This invention relates to electrolytic condensers, 4and its chief objectis to provide a compact condenser of good efliciency, which can bemanufactured at low cost. To this and other ends )the inventioncomprises the 'novel features and combinations hereinafter described.

While the invention can be employed in various situations the advantagesabove mentioned make it especially useful in radio apparatus, as forexample as a smoothing condenser in devices for eliminating the ripplein rectified'alternating current, and accordinglv I have selected forillustration and .15- specific description herein an embodiment designedparticularly for the purpose named. In this form it is easily possibleto construct a condenser of cylindrcal shape not more than two and afourth inches in diameter and four inches in length, having a capacityof fifty microfarads. The anode, composed of alu'- minum or thenmetalcapable of forming the necessary dielectric film on its surface, may bea stripof sheetl metal fastened to and 5 wound spirally around a stiffrod of the same metal. This rod may form the anode terminal. The turnsmay be spaced apart in any convenient and suitable manner, t0 permitvcirculation of the electrolyte, as for examo ple by indenting the sheetmetal to form numerous lugs on one side of the same. The anode, inwhatever -form it is made, is immersed in a siutable electrolyte, say anaqueous solution of boraX and boric acid, vin a cylindrical vessel ofsheet copper, which may serve as the cathode. One embodiment of theinvention is illustrated in the accompanying drawing, in which Fig. 1shows one end of an indented sheet metal strip before ceiling.

Fig. 2 is a section on line 2-2 of Fig. l. Fig. 3 shows one end of thestrip fastened to the rod around which it is to be coiled.

Fig. 4 is a section on line 4 -4 of Fig. 3. Fig. 5 is a side view of thecomplete anode. Fig. 6 is a. section on line 6-6 of Fig. 5.

on line 7 of Fig. 5.

Fig. 8 shows the complete condenser, partly in section.

The aluminum strip 10, Fig. 1, may be of any suitable thickness, 0.006of an inch being satisfactory for a condenser of the size and capacitymentioned above. Along one edge, or both if desired, are three rows ofindentations parallel to the edge, forming three rows of small lugs orbosses 11. Those in the upper and outer row are on, or protrude from,one side of the strip and those inthe middle row are on the other side,as clearly shown in Fig. 2. The rest of the strip may be indented, inthe same or in any other convenient pattern, but if the lugs areelongated, as shown at 12, forexample, I prefer to make them in diagonallines, as being less apt to cause the spiral turns of the strip, incoiling it around the center stem or rod, to take polygonal crosssection. I also prefer separated lugs rather than continuous ribs, aspermitting freer flow of convection currents in the electrolyte. In anycase the lugs or, generally, the spacers, are preferably as sharp aspossible, and in some cases it may be advantageous to make theindentations in such manner as to actually perforate the inetal,producing sharp edges as indicated at 12a, Fig. 2, or 11a, Fig. 7, sothat when the strip is coiled the point of contact between the apex ofthe lug and the adjoining turn or convolution will have a very minutearea. as I have found that the smaller the area of contact the lessopportunity there is for corrosion at such points.

The aluminum rod 13 is split for a portion of its length to receive theend of the strip 10, which is welded to the rod along its end edge. Thestrip is then coiled around the rod in spiral form, the lugs or spacersholding the turns apart to permit access of the electrolyte to all partsof the spiral anode thus formed and to allow free circulation of theelectrolyte. The three parallel rows of lugs or spacers at the upperedge interlock, as it were, in the manner indicated in Fig. 7, and thusserve to llimit the axial displacement of the turns. Otherwise a slightstress exerted axially might distort the device into a pro- 60' negativeterminal nounced conical form, as will be readily understood. I

The container or tank for the electrolyte and anode may be a cylindricalvessel 14, 5 Fig. 8, of suitable non-filming sheet metal. fFor economyof space the tank may be ]ust large enough to receive the anode and,preferably, leave room for an insulating lining or other means toprevent electrical Contactbe- 16 tween the anode and the tank. Otherwiseit may be desirable to wrap the anode with one or more turns of filmingwire (not shown) to prevent expansion of the spirally wound strip. Itwill be understood, however,

l that since the film formed on the anode is) non-conducting the anodemay bear directly against the vessel without shorting the com denser aslong as the film is in good condition. The insulatingI lining preventselectrical contact if the film should be worn olf by friction or beotherwise impaired. A lining for the purpose indicated may consisty of abottom disk 15 of thin Celluloid orL cellophane and a strip 16 of likematerial bent to cylindrical form and placed loosely in the vessel,Celluloid and cellophane being unharmed by and harmless to theelectrolyte.A The vessel metal anode, an electrolyte4 1n which the maybe- Closed by a disk 17 of insulating material resting on a bead 18 onthe inside near 3G the top. Around the closure at the edge is a thinflat ring or gasket of rubber or other suitable material, and the edgeof the vessel is crimped or turned in and down upon this gasket, forminga. seal. A vent hole 19 is. 'provided in the cover 17. This can beplugged with wax to prevent spilling of the electrolyte in shipment andhandling. When the condenser is put into service the wax can beperforated with a pin to permit escape of any 4o gases resulting fromelectrolytic action in the electrolyte. Orthe usual disk of thin sheetrubber can be cemented over the vent hole. hen punctured with a pin thedisk serves as an automatic valve, opening when the v '45 pressure ofthe gas rises inside the tank and closing as soon-as the pressure isrelieved. The tank ispreferably deep enough, as in Fig. A8 for example',where the dotted line 20 indi-` s Cates the surface of the electrolyte,to permit sea substantial depthof electrolyte above the anode. Thereserve thus provided takes care of the slow loss by electrolytic.decomposition and in most cases makes it unnecessary to provide thevessel with a filling aperture and a removable closure therefor. l Y

The rod 13, threaded on its upper end, extends through the lid 17 toform the positive terminal and isclamped to theelid by nuts 21 setupfirmly on yielding gaskets 22.. The

may be a screw 23 on a bracket24 soldered to the can 14. f

'Ifhe electrolyte is preferably the one described in my Patent No.1,141,402, issued June 1,-1915,' compounded -in the following C'proport1ons: saturated borax solution ('distilled water), two gallons;boric acid, three pounds; and an additional half-pound of borax. f

The necessary film can be formed on the anode in any suitable manner, asfor example by the methodsv described in my prior Patents Nos. 1,012,889of December 2 6, 1911, andl 1,388,874 of August 30, 1921. Preferably thelm is formed at such voltage as will permit the 'condenser to withstanda substantial operating voltage, say 400. I

It is to be understood that the invention 1s not limited to the specificconstruction herein illustrated and described but may be embodied inother forms without departure from its spirit. The anode shown forms nopart of the invention, since any suitable type of anode may be used,preferably made of sheet metal so disposed as to have a large area ofContact with the` electrolyte. rlhe anode described herein is claimed inmy copending application Serial No. 78,534, liledy December 31, 1925,now Patent No. 1,7 7 3,492,

issued August 19, 1930, of which the present application is a division.

Iclaim- 1". In an electrolytic condenser, a filmed anode is immersed, anunlmed metal cathode surrounding the anode and in Contact v.with theelectrolyte, and a sheet of exible non-conducting material, harmless tothe electrolyte and unharmed thereby, surrounding the anode between thesame and the cathode. f

2. ln an electrolytic condenser, an electrode comprising a strip offilmed metal bent s pirally, an electrolyte 4in which the anode isimmersed, aeCurrent-Carrying member of nonlming metal surrounding thespiral anode and in Contact with the electrolyte, and a iiexible sheetof Celluloid around the immersed spiral anode between the 'same and thenon-filming metal member. A

3. In an electrolytic condenser, a cathode ice' of non-filming metal inthe form of a coni taining vessel, an electrolyte therein, an anode offilming metal immersed in the electrolyte and a lining ofsheet Celluloidin the vessel b electrolyte.

4.,In an electrolytic condenser, an anode of filming metal, anelectrolyte in which the anode is immersed,a cathode of non-filmingsheet metal in the form of a vessel enclosing the immersed anode, and aNsheetbf flexible Celluloid around the anode between the sameandthecathode. i

In testimony signature.

RALPH D. MERsHoN.

etween the same andthe immersed f whereof I` heretoI aixmy

